There is a small speaker inside your box - you can remove it or unplug the little cable that is plugged in. Although this may sound a bit drastic I still think it is the best way to deal with the annoying beeping problem.

If you don’t want to go that route this is what you should do:
Open Control Panel -> Sounds and Audio Devices -> click the Sounds tab -> from the drop-down menu of Sounds Scheme choose No Sounds.